Piston dynamics analysis considering skirt-liner dynamic clearance

Piston slap force is one of the main sources of mechanical engine noise. To obtain a more accurate determination of the piston slap force and minimize piston slap noise, a new simulation model that considers dynamic clearance of the piston skirt and liner has been established in this study. The skirt-liner dynamic clearance is caused mainly by the elastic deformation and thermal deformation of the piston. Comparing three different models, it was found that the impact of dynamic clearance on the piston slap force is reflected mainly in the medium-high frequency, which is the sensitive frequency of the slap noise. Therefore, it is necessary to consider dynamic clearance in the simulation model. In addition, the mechanisms behind the dynamic clearance effect on fluid lubrication, piston dynamics, and piston slap noise were observed. In particular, three typical structural parameters in piston dynamics (the piston pin offset, piston-liner clearance, and piston skirt profile) were studied. The analyses provide guidance for the design of low-noise engines.